Sharks saved in Marine Protected Areas?

A recent research study by Knip and fellow researchers (2012) published in the journal Biological Conservation, evaluated a Marine Protected Area (MPA) for the conservation two species of coastal sharks. The scientists studied the movement patterns of the sharks and determined how much time they spent in the recently established MPA, the Great Barrier Marine Park in Australia. Before I discuss their results with you, we should go over some basic background information.

What is a Marine Protected Area?

A Marine Protected Area (MPA) is an area of ocean or coastline where human activities are restricted. The restrictions in an individual MPA may vary with the specific goals and objectives of that particular MPA. For instance, some MPA’s restrict all human activities, including tourism. This type of MPA can be called a “sanctuary” or a “reserve”. Other MPA’s may only limit fishing and exploitation during a specific season or for a certain species. Most often, MPAs are created to ensure the conservation of some or all species, habitat, and/or resources within them.

In 2010, the International Union on the Conservation of Nature (IUCN) estimated that there are roughly 5880 MPA’s, covering nearly 1.2% of the world’s oceans. This is an increase of over 150% since 2003.

A common criticism of new MPAs is that they are implemented with little prior knowledge of how well they will protect habitat or species in the given area. This is because within one MPA there can be many habitat types, from lagoon and coral reefs, to the open ocean. Managing all of these habitat types and the species that live within them can be a daunting task. Also, it can be hard to estimate how effective the MPA is for the conservation of a specific species, or groups of species such as sharks. What measure scientists use to estimate effectiveness is also important. Should effectiveness be based on the amount of time a species spends in the MPA, much much area of the total MPA they use, or some other measure? What is important to remember is that any protection is better than nothing and all MPA’s provide some amount of conservation protection.

To successfully manage a MPA, partnerships and collaboration between local citizens who use the resource and conservation groups, the government, and sometimes private businesses are needed. Who is involved really depends on the goal of the MPA.

Sharks are a mobile species. What does that mean?

Many shark species use a lot of different habitats throughout their life. Some are born in shallow coastal areas but leave once they grow up. For example, lemon sharks are born in shallow lagoons often near mangrove forests. When the sharks reach 2 to 3 years old they will venture out into the larger coastal zones of the ocean. We call these species mobile because they travel between many different habitats. There are some sharks though, like the spottail in the study we’re going to talk about, that stay close to shore for their entire lives.

Sharks and MPA’s

Most of the research on the effectiveness of a MPA has been based on sedentary species. That is, species that don’t move around a lot, such as a clam. So, we could protect a clam and their habitat relatively easily by putting a small MPA around the habitat they live in.

Planning and managing a MPA for sharks is complicated. In order to maximize the benefit of the MPA to a shark species we need to know what type of shark we are trying to conserve, are they more or less mobile, what life stage will use the MPA, and so on. Through their research, discussed below, the scientists asked this type of question: Does a new MPA within the Great Barrier Reef Marine Park offer conservation benefits for two species of sharks, the pigeye and spottail?

What does the research show?

Knip and fellow researchers looked at whether a MPA on the Great Barrier Reef in Australia was beneficial for two kinds of sharks, the pigeye and spottail. The pigeye is a large shark that only uses the coastal area as a juvenile and the spottail is a medium sized shark and stays in the coastal area for its entire life. Both sharks are known to use the coastal area where the new MPA was established. Fishing is restricted (but not forbidden) in the MPA, so the sharks are able to reproduce and grow up to a reasonable size before they must face the big ocean, and potentially more fishermen.

The researchers tagged sharks and tracked their movements to see how often they used the MPA. Based on how much time the sharks spent in the MPA the researchers could say if the MPA offered a conservation benefit to them. The researchers found that both of the sharks DO use the MPA and even though the pigeye leaves and comes back, it is likely offering a conservation benefit by having the MPA as a refuge. They also found that the pigeye sharks usually left and entered the MPA at the same ‘exit points’. Like taking the same path through a forest each time you’re out for a hike. This kind of information can be very helpful for MPA managers because they might be able to provide enhanced protection in high use areas.

Conservation managers can use the results of studies like this of to help improve existing MPAs and plan new MPA’s that are more effective to help shark conservation.

How to you TRACK a shark?

By now you’re probably asking: HOW do you track a shark?! It takes a lot of work, but it can be very fun! While volunteering with the Bimini Biological Field Station in 2003, I participated in a study that was looking at the movement patterns of young lemon sharks. We used a tracking method similar to the study by Knip and others. First of all, you have to catch the shark. We used nets, while Knip and fellow researchers used baited hooks to capture the sharks, but neither method harms the sharks. Once captured an ‘acoustic tag’ is attached to the shark which sends out a pulsing beep in a particular sequence, say 2-3-2, that a special kind of receiver (underwater computer) can hear. Once the shark is released, anytime it comes within a certain distance from the receiver, the shark is recorded as being nearby. We call this passive tracking because receivers are placed at several places and we hope the shark swims by. Tags that send data to satellites in real time are also very popular for passive tracking.

Here are some resources if you’re interested in learning more about MPA’s

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[…] benefit, just like when a marine protected area focuses on shark conservation (see our blog on Sharks Saved in Marine Protected Area?). Some of these other species may not get protection on their own because they are not known to […]

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